The so-called “hybrid” engines comprise an internal combustion engine and an electrical part which comprises at least one electric starter.
In the supercharged internal combustion engine, fresh air is introduced into an intake duct and is compressed by a compressor of a turbocharger, before being routed to an intake manifold linked to a combustion chamber of an engine cylinder via an intake valve.
After combustion, the residual exhaust gases are expelled toward an exhaust duct through an exhaust valve and drive a turbine driving said turbocharger placed in this exhaust duct.
The internal combustion engine produces polluting exhaust gases, notably comprising carbon monoxide, unburned hydrocarbons, particulates and nitrogen oxide molecules.
In the “hybrid” engines, provision is made, in order to limit these polluting emissions, to stop the internal combustion engine when the speed of the engine is lower than a predetermined threshold, then to restart it using the electric starter.
Thus, the internal combustion engine is stopped automatically, without the intervention of the driver, for example when the vehicle is stopped at a red light.
The emissions of polluting exhaust gases are thus limited.
However, when the internal combustion engine is stopped in this way, the oil circulation of this engine is also stopped and the central housing of the turbocharger is no longer cooled by this oil circulation. If the automatic stopping of the engine is initiated while the temperature of the exhaust gases circulating in the turbine of the turbocharger is very high, these exhaust gases may provoke a rise in temperature of the central housing of the turbocharger which is damaging to the operation thereof.
In particular, the coking of the oil present in this central housing at high temperature produces a solid residue which may block the rotation of the shaft of the turbocharger. Exceeding the thermal resistance limits of the materials may also damage the operation of this turbocharger.
In order to limit the increase in the temperature of the turbocharger associated with the automatic stoppages of the internal combustion engine, it is known to use an additional water pump, fed by the electric part of the engine, to cool this turbocharger when the internal combustion engine is stopped. However, installing such a pump is costly and its use increases energy consumption.